Telegraph switching system



June 4, 1940. w. J. ZENNER 2,203,289

TELEGRAPH SWITCHING SYSTEM Filed Oct. 22, 1957 a Sheets-Sheet 1I'NVENTOR. WALTER J. ZENNER BY Y ATTORNEY.

June 1940- w; J. ZENNER TELEGRAPH SWITCHING SYSTEM 3 Sheets-Sheet 2Filed 001:. 22, 1937 INVENTOR. WALTER J. ZENNER ATTORNEY.

BY ww 4 June 4, 1940.

w. J. ZENNER TELEGRAPH SWITCHING SYSTEM 3 Sheets-Shet 3 Filed Oct. 22,1937 INVENTOR.

WALTER J. ZENNER ATTORNEY.

ifatet' teti June 4, 1940 UNITED STATES TELEGRAPH SWITCHING SYSTEMWalter J. Zenner, Des Plaines, Ill., assignor to Teletype Corporation,Chicago, 11]., a corporation of Delaware Application October 22, 1937,Serial No. 170,376

7 Claims.

This invention relates to telegraph systems and more particularly tosystems and apparatus therefor capable of selectively interconnectingtelegraph stations for communication.

An object of the invention is the provision of telegraph selectorapparatus responsive to permutation code signals for interconnectingline conductors for telegraphic communication.

A further object of the invention is the provision of instrumentalitiesat a central station for enabling a subscriber at any one of a pluralityof substations to connect the telegraph apparatus thereat with any otherdesired station of the system without the intervention of an operator.

The above and other objects of the invention are attained by theprovision of a selector mechanism including instrumentalities responsiveto permutation code signals for setting, in accord ance with suchsignals, a plurality of permutation or code bars. These code bars serve,upon their permuted setting, to select selectable elements which, bymeans of bell crank levers controlled thereby upon the operation of auniversal bail, close contacts individual thereto. These contacts areincluded in circuits extending to other stations equipped with printingtelegraph apparatus, which is adapted to be connected through suchcontacts to other stations of the system. The contacts, throughprovision of a latch mechanism, are maintained closed until apredetermined selection is established, which operates mechanism wherebythe several latch mechanisms are operated and all of the previouslyoperated contacts are restored to their normal or open position. Whilethe selector apparatus serves to interconnect, through its contacts, theline conductors of the printing telegraph stations, its selectormechanism responds to the impulses impressed on the interconnecting lineconductors but is ineffective on the selector mechanism sinceinstrumentalities responsive to a particular signal are provided forrendering all selectable elements unresponsive to the permuted settingof the permutation bars, except for one selectable element whichresponds to a particular signal for-restoring the selector to aselective condition. Through the recited contacts, the line conductorsmay be connected either directly or through the contacts of relayscontrolled from the contacts on the selector apparatus.

The above and other objects and features of .the invention will now bedescribed in detail with reference to the accompanying drawings inwhich,

Fig. 1 illustrates, in end elevation, a selector apparatus embodyinginstrumentalities for selectively interconnecting the line conductorssin- 5 gly .or in groups;

Fig, 2 shows diagrammatically the selector apparatus shown in Fig. 1 asit may be arranged at a central or switching station; and

Fig. 3 shows diagrammatically the arrangement 10 of several substationsand the lines interconnecting such substations with the central stationembodying apparatus as exemplified in Fig. 2.

With Figs. 2 and 3 positioned with Fig. 3 below Fig. 2, a substantiallycomplete system is disclosed.

The selector apparatus disclosed in Figs. 1 and 2 is similar to andembodies many of the features disclosed in Patent No. 1,745,633 grantedFebruary 4, 1930, to S. Morton et al. Conse- 20 quently, the disclosureof the Morton et al. patent is incorporated herein by reference as apart of the present specification, and for details of the selectingapparatus not specifically disclosed herein, reference should be had tothe cited 25 Morton et al. patent. It is, however, to be understood thatthe invention is not limited to the particular type or form of selectorapparatus disclosed in the cited Morton et al. patent, for it ismanifest that other forms and types of select- 30 ing apparatus might beused with equal satisfaction to the particular selector apparatus chosenfor illustration of the present invention.

As disclosed in Fig. 2, the selector apparatus is located at a centralstation. It is, however, 35 manifest that such apparatus may be locatedat any one of a plurality of stations, which may not necessarily bedesignated as a central station. As disclosed in Fig. 3, particularlywhen arranged immediately below Fig. 2, a plurality 40 of subscriber'sstations 5, 6, I, 8, 9, I0, and II are connected through line conductorsL5, L6, L1, L8, L9, LIO, and Lil to the selector relays.

At each of the indicated stations, except station II, a receivingprinter R and a transmitter T 5 are located. At station It only atransmitter T is disclosed. It is, of course, understood that areceiving printer might also be located at station ll if it is desiredthat such station should act also as a station for receiving communica-50 tions from other stations. Also, at each of the stations, there is adriving motor M, which supplies power for driving the elements of thereceiving printer R and the transmitter T. The motor at each of thestations may be driven from a local source of alternating currentapplied through either a manually controlled switch, such as 25, or thecontacts of a remotely controlled relay as disclosed for station Ell. Inthe case of station it, the circuit for its driving motor will benormally open at the contacts of its control relay, whereas theoperating circuit for the driving motor at the other stations will becontrolled by the local attendant, and at such stations the drivingmotor will run continuously if there is any likelihood that a message isto be destined for such station,

The selector at the central station, which serves to connect, throughthe contacts controlled thereby, the line conductors of the severalrecited stations, embodies a driving motor 21 which drives, throughgears 28 and 29, a shaft 35 which, through positive clutch 3|, drives acam sleeve including an operating cam 32. Power from shaft 30 is alsocommunicated to cam barrel or sleeve 33 through a friction clutch 34. Asis fully described in the cited Morton et al. patent, the cam barrel orsleeve 38 is normally held against rotation, but rotates in response tothe deenergization of the electromagnet 35 when it responds to the startimpulse for setting, through the T- levers 36 and the transfer elements31, the code bars 38 in accordance with the signals impressed on theelectromagnet 35, which, in turn, causes the corresponding operation ofthe selector mechanism of the apparatus as is fully disclosed in thecited Morton et a1. patent.

In the particular selector apparatus disclosed as a part of the presentinvention, there are seven code or permutation bars 38. Five of thesebars are positioned directly in response to the operation of theselector unit of the apparatus, whereas the other two bars respond toparticular groups of code signals. For example, one of the two code barsresponds to a code signal to render the other code bars ineffective forselective Purposes, except for one particular signal combination, whichis utilized for restoring the selector to its normal position. The othercode or permutation bar responds to shift and unshift signalcombinations; that is, it is moved in one direction in response to ashift signal and in the other direction in response to an unshift signalfor the purpose of expanding the selective possibilities of the selectorapparatus.

As illustrated in Fig. 2, the permutation bars 33 are slidably mountedon a plate 39, which has its forward edge, as viewed in Fig. 2, notchedto provide a guide comb for a plurality of selectable or pull bars 40arranged with their upper ends to cooperate with the permutation bars 38and to be selected in response to the various permuted settings of suchbars. Inchvidual to each of the pull bars 40 is a spring 4|, which tendsto move its pull bar downwardly and rearwardly and hold it in normalposition, as shown in full lines in Fig. 2, with the forward restrainingedge of a common operating or striker bar 42 against an edge of each ofthe pull bars 40.

As shown in Flg. l, cam 32 cooperates with a roller 43 carried by arm 44rotatable on pivot shaft 45 to which is also mounted lever 48 connectedthrough link 41 to the lower part of common operating or striker bar 42.Operation of lever 43 in response to the rotation of cam 32 will occurcyclically with the operation of cam drum 33 due to the action of a camthereon (not shown) with pivoted release lever 43, which has its freeend moved out of the path of a stop lug 58, which permits spring to movethe driven portion of clutch 3| into operative relation with the drivingportion thereof. Power is thus communicated by cam 32 and through lever44 and timed relation to the setting of permutation bars 38 to allow forthe selection of pull bars 40.

Normally, cam 32 is held against movement and holds, through levers Q4and 46 and link 41, striker bar 52 in its lowermost position withsprings ll under tension. In this position, the upper end of each of thepull bars 40 is held in front of but spaced slightly from the notchedforward edges of the permutation or code bars 38. When the latter areset in accordance with any received signal, cam 32 is rotated, and,through levers 44 and 48 and link 41, striker bar 42 is raised andlowered. If the latter moves upwardly, the springs 4| move the bars 48rearwardly against the notched edges of the permutation bars 38, and oneof the bars corresponding to the setting of the permutation bars dropsinto the notches of the latter far enough to bring a rearwardlyprojecting lug 53 thereon into the path of movement of striker bar 42.Upon the continued upward movement of bar-42, its forward edge engagesthe lug 53 of the selected bar 40 and moves it upwardly, thereby movingthe lower edge of such bar correspondingly. When a bar 48 is engagedwith the notches 'of the permutation bars 38, the latter are lockedagainst adjustment, but as the striker bar 42 returns to its normalposition, it engages a cam surface formed on the rear edge of ,each ofthe bars 40 and moves all of such bars clear of the permutation bars 38.The latter are then ready to receive a new setting as previouslydescribed.

The lower end of each of the .bars 48 is formed with a hook 56, whichengages one arm of a bell crank lever 51, the other arm of whichservesto operate a pair of normally open contacts 58, the purpose of whichwill be described later. Cooperating with the arm of the bell cranklever 51, through which the contacts 58 are closed, is a spring operatedlatch 59 arranged in such manner that upon the operation of any of thebell crank levers 51 in a counterclockwise direction, as viewed in Fig.2, the contacts will, through latch 53, be held in their operatedposition.

Common to all of the latches 59 is a bail 50, which extends transverselyof the selector apparatus as disclosed in Fig. 2. Ball 68 is pivoted atits opposite ends in the side frame of the selector apparatus and hassecured at its righthand end a lever 8| normally under the tension of aspring 82 to move its free end into the path of the hook portion of aparticular pullbar 83, which responds to a predetermined setting of thecode bars 38. When such predetermined setting of the code bar 38 isestablished and the striker bar 42 operates, as previously described,pull bar 83 likewise operates and, through lever 3|, operates ball 88 tooperate all of the latches 53 to the position shown in Fig. 2 free oflatching engagement with the bell crank levers 51, so that each of suchlevers will be restored to their normal unactuated position by thetension of one of the springs of the pair of contacts 58.

n is highly desirable, following operation of or more of the bell cranklevers 51, to establish a 1 condition whereby the selector apparatuswill not respond to the code combination of impulses impressed on itse'lectromagnet ll, except for a particular code combination which may beallocated to the function of restoring the. selector to its normalposition. To accomplish such a result.

blocking bar 88 is provided. This blocking bar is operated by a springtensioned lever device 81 arranged with horizontally extending arms 88and 88 the forward ends of which lie in the path of certain ones of thepull bars 48. Specifically. arm 88 lies in the path of pull bar I8 andarm 88 lies in the path of pull bar 88. Consequently, when these pullbars 88 and I are operated, and provided lever device 81 is in aposition to receive movement from either of the bars, the blocking bar68 will'he moved to a position dependent upon which of the arms 88 and88am engaged by the respective pull bars 68 and I0. As disclosed in Fig.2, lever device 81 has its arm 68 positioned to be engaged by pull barIII. When such pull bar is operated, its upper end engages arm 68 androtates latch device 81 about its pivot and allows the spring attachedthereto to move bar 68 to the left as viewed in Fig. 2. When in suchposition, bar 88 blocks all of the pull bars 40 but allows the operationor pull bar 88 in response to a particular code combination of impulses.Under such conditions, arm 88 is now in the path of the upper end ofpull bar 88 and will be engaged thereby upon the operation of such pullbar. Lever device 61 remains in its set position due to its frictionalengagement with its pivot screw.

Also, grouped with the permutation bars 88 is a code bar I3 arranged tobe shifted right or left through a lever device I4 similar inconstruction to lever device 61 and provided with horizontal forwardlyextending arms I5 and I6, which lie in the path of pull bars 11 and I8identified with shift and unshift signal code combinations,respectively. That is, when the code bars 38 are positioned inaccordance with a shift signal, pull bar 11 will be selected, and uponits operation will move code bar II to the left, as viewed in Fig. 2,through the lever device II which remains in its set position due to itsfrictional engagement with its pivot screw. Likewise, upon the operationof pull bar 18, lever device I4 will be operated and code bar I3 will berestored to the position shown in Fig. 2. With the code bar I3 in itsrespective left and right-hand positions, the permuted arrangement ofthe code bars 38 will be altered to accommodate a larger number of pullbars 48 with a five unit code. In other words, such an arrangementexpands or doubles the selective possibilities of the basic five unitcode.

Also operated by lever device II is acontact spring I9, which may engageeither contact spring 88 or contact spring 8| depending upon theposition of code bar I3.

As shown in Fig. 1, there is also mounted, on the base plate supportingthe motor 21 and the other parts of the selector mechanism, atransmitting unit 85 including a transmitting cam shaft 86 and aplurality of contacts 81 arranged to be operated in sequence in responseto the rotation of the cam shaft 88 and conditions established for theiroperation. Power for driving cam shaft 86 is supplied from motor 2I andsuitable shafts and gears through a positive clutch 88, which isarranged to have its driven and driving portions in engagement inresponse to the energization of an electromagnet 89 provided with anarmature 8i!v cooperating with a stop latch 9i, which, upon theenergization of electromagnet 88, is moved out of the path of stop lug82 and allows the engagement of the driven portion of clutch 88 with thedriving portion thereof, and thus the communication of power to camshaft or sleeve 88. The transmitting unit 85 may be used for the purposeof transmitting signals indicating the proper interconnectio'n'pfdesired line conductors.

Referring now to Figs. 2 and 3 arranged as previously indicated withFig. 3 below Fig. 2, it

is seen that the conductors l8 ,l8, ll. l8, l8, and

28 extend to contacts 58 of the selector apparatus located at thecentral station. Included in each of these conductors and preferablylocated at the central station or the station at which the selectorapparatus is located is a relay 83, 84, 85, 88, 81, and 88,respectively, which are arranged to have their energizing circuitsestablished in response to the operation of the contacts 58 individualthereto. That is, there is a set of contacts 58 individual to each ofthe conductors I5 to 20, inclusive.

As disclosed in Fig. 2, the contacts 88 are grouped and may be referredto as shift and unshift contact groups. That is, depending upon theposition of code bars I8 and contact spring I9, ground will be appliedto the respective groups of contacts. With the code bar I8 in theposition shown in Fig. 2 where contact spring I8 is in engagement withcontact spring 8|, ground is applied to the left-hand or unshift groupof contacts 58. With code bar I3 in its other position, contact springI8 will be in engagement with contact spring 80 and ground will then beapplied to the other or shift group of contacts. In that way, thecircuits for the relays 93 to 98, inclusive, are controlled.

In the operation of the system disclosed and the apparatus thereof, letit first be assumed that the subscriber at station 5 desires to beconnected to subscriber at station I, the line L6 of which extends tothe right-hand front contact of relay 84, and-further that the selectorapparatus is in its shifted position or the position wherein contactspring I9 engages contact 80.

The motor switch at station 5 is normally closed during business hoursso that the motor M of such station is energized by the power sourceprovided for that purpose. It is also to be assumed that motor 21 of theselector unit located at the central office is also running, and thatthe selector unit is in a condition for the selection and operation ofits various pull bars. Accordingly, a subscriber at station 5 transmitsby means of transmitter T a combination of significant current impulsesover line conductors L5 and L6 to the central office over line conductorLil and conductors 2| and 22. At the central oillce, the preassignedcombination of significant current variations is received by receivingmagnet of the selector unit-which operates the selecting unit forselecting a particular pull bar 40. Pull bar 40 is operated, aspreviously described, by bail 42 in a manner to operate bell crank lever51 associated therewith, which, when operated, will be latched by latch58 against the tension of its retractile spring to hold contacts 58closed pending the receipt of a significant code combination of impulsesto effect the operation of restoring bail 60 and restoration of all ofthe operated bell cranks 51 to normal or the position shown in Fig. 2.

In the description immediately above relative to the closure of contacts58 through the operation of the selector unit, it was assumed that theselector unit was in a condition to permit the operation of any oi thepull bars II, and iurther, that the code bar ll was in a position withcontact spring II in engagement with contact Iii. However, to insurethat the selector unit was in'a condition to selectively operate thecontacts 88, the code signal combination signincant ior connecting lineI in an operative circuit with station I should be preceded by signalcombinations, which eflect the operation oi a blocking bar 66 to aposition where the pull bars Iii are iree to be selected by thealignment oi the notches in the code bars 88. As previously described,blocking bar 88 is operated through the operation oi pull bar 08 andlever device 61. with blocking bar OI in the position shown in Fig. 2.any oi the pull bars ll may be selected.

Upon the closure oi contacts 99, a circuit is completed for theenergization oi relay 9! extending from grounded battery, winding oirelay 99, conductor l5, closed contacts 98, conductor 99. contact 90,and contact spring I. to ground. Relay 9! is energized and as a resultof its energization operates its several armatures. Through itsleft-hand armatures the line conductors oi station I are connectedserially with conductor LII in circuit with which station I, throughconductors L5 and L6, is connected. Through the right-hand armature oirelay II, a locking circuit therefor is established extending fromgrounded battery, winding of relay ll, right-hand front contact andarmature thereoi, conductor I00 and normally closed contacts I toground. Relay 93 thus is maintained energized independently oicontactsII. It is, however, assumed that a locking circuit ior such relay mightnot be required since latch Bl maintains, through hell crank lever 51,contacts ll closed pending the receipt oi a code combination of impulsesto eflect the operation oi restoring ball 60.

With the operation of relay 98 as described, the operating circuit forstation 6 extends irom grounded battery at station 5, normally closedcontact of transmitter T, the selector magnet of printer R, lineconductor LI, selector magnet R and the closed contact oi transmitter Tat station 6, line conductor L8, normally closed right-hand contacts oirelay 9, contact I" and armature of relay 93, right-hand conductor oithe line conductor L'I, selector magnet oi the printer R, closed contactoi the transmitter '1 at station I, the leit-hand line conductor L'l,armature ,and contact llli oi relay 99, line conductor Li I, normallyclosed contact oi transmitter T at station ii, conductor 22, winding oiselector magnet oi the selector unit at the central station, conductorII and the extreme left-hand armature and back contact oi relay 96 tothe opposite terminal oi battery.

Since the subscriber at station I normally has switch 25 closed duringbusiness hours, the motor M at such station will be energized at thistime by current from the local source oi power. Accordingly, the systemis now in condition ior communication to take place between thesubscribers at stations 5 and I with the printing telegraph apparatus atstation 6 responding to impulses impressed through the operation oi thetransmitter at either station 9 or I provided the motor at stationj isoperating.

As described, the electromagnet 35 of the selector unit at the centraloillce is included in the circuit connecting stations I, I, and I.0onaequently. the selector magnet II will iollow the significantimpulses or code combinations oi not respond to the operation oi thetransmitter at the respective stations iollowing the establishment oi aconnection unless it is desired to connect additional stations to theintercommunication circuit. To prevent the operation oi the pull bars lliollowing the establishment oi a connection or connections with desiredstations and notwithstanding the iact that the selector magnet II andits component elements will iollow the signals impressed upon thecircuit traced ior stations I and' I, blocking bar 09 is provided. Thisblocking bar. as previously described, responds to the operation oi pullbar II in response to a combination oi impulses transmitted from stationI iollowing the selection oi station 1, whereby it is moved to the ieit,as viewed in Fig. l, to a position where all oi the pull bars oi theselector unit, except pull bar I, are prevented irom dropping into thenotches oi the permutation bar It notwithstanding the iact that suchpermutation bars are operated, and in operating the notches therein arealigned ior the selection oi pull bars ll. With such a construction, thepermutation bars II respond to the signals impressed upon theelectromagnet II, but no selection oi a pull bar 49 is eiiected sincethe blocking bar 09 prevents their selection.

When the intercommunication between subscribers i and I has beencompleted, the subscriber at either station may send a group oi codecombinations oi impulses ior operating the selector unit at the centralstation to eiiect disconnection of the interconnected lines of therespective stations. Such disconnection results irom the deenergizationoi relay 9! and/or the opening oi the contacts ll associated with suchrelay. To achieve such results, a significant signal is transmitted tothe selector unit ior eflecting its operation to cause the selection andoperation oi pull bar 63, which, when operated by striker bail 42 iromcam 91, rotates lever ii about its pivot to cause the correspondingrotation oi bail ll through which all oi--the latches it are rotated ina'clockwise direction against the action oi their retractile spring.-Thus,

latches II, which may be holding bell crank levers 51 to maintain theclosure oi their associated contacts 59, are operated suillciently toallow bell crank levers II to be restored to their normal position bythe action oi the retractile spring individual thereto. Simultaneously,with the operation oi pull bar I upwardly, normally ciosed contacts III!are opened removing the ground connection irom the locking circuit ofrelay .3. Relay '8 thus is deenergized and restores the circuitconnections to the condition shown in Fig. 3.

The operation oi pull bar .3, also through levar device 61,specifically, its engagement with arm 09, causes the blocking ball 68 tobe moved to the right as viewed in P18. 2 or to the position shown insuch figure to allow subsequent selection and operation oi pull bars 49.

Let it now be assumed that station 5 desires to be connected to stationll. As shown in Fig. 3. the operating circuit of motor M at station IIis controlled through the right-hand contacts oi relay ll, and iurtherthat the line circuit Lil oi station "is controlled by relay It. Inorder to eiiect the connection oi station it in circuit with station 9,it is necessary for station 5, assuming that the motor oi such stationis normally running, to transmit a group of impulses identified with thepull bar 49 of the selector unit allocated to the control of relay 99followed by a group of impulses identified with the pull bar 49allocated to relay 99. Upon the transmission, through the operation oftransmitter T at station 5 of a group of impulses identified with thepull bar individual to the contacts associated with relay 99. a circuitis established for the energization of relay 99 extending from groundedbattery, through the winding of relay 99, conductor I9, contacts 59 nowclosed, conductor I94, contact 9|, and contact spring 19 to ground. Ofcourse, in such explanation, it is understood that the selector unit isin its unshiited position or a position where contact 9I is engaged bycontact spring [9. Relay 93 is thus energized and a looking circuittherefore is established through its middle front contact and armatureto ground at contacts I93. Upon the energization of relay 99, theprinting telegraph apparatus at station I9 is included in circuit withthe printing telegraph apparatus at stations 5, 9, and 9. However, as tostations 6 and 9, it may be assumed that the motor switch at each ofsuch stations is normally open, which removes power from the operatingmotor at each station and renders the printing telegraph apparatusthereat non-responsive to signal impulses, which may be impressed on theinterconnecting line conductors. Of course, it the motor switch at eachsuch station is closed, the operating motor thereof will be running andthe receiving printer thereat will respond to the impulses impressedupon the interconnecting line conductors.

The operating circuit of the motor M for sta tion I9 is remotelycontrolled, as distinguished from locally controlled, as exemplified bystations 5, 9, and 9 Consequently, it is necessary to follow the groupof impulses, which efiected the operation of the pull bar allocated torelay 96 with a group of impulses for operating the pull bar 99allocated to relay 99. When such operation occurs, which is similar tothat described for the operation of pull bar, which eflected theenergization of relay 96, relay 99 is energized and locks up overcircuit I09 through contacts I93. Through the right-hand armature andfront contact of relay 99, a circuit including conductors 23 and 24 andmotor M of station I9 is completed. Motor M thus is started and makespossible the operation of the printing telegraph at such station.

Before intercommunication is commenced between the stations 5 and I9,assuming that stations 6 and 9 are not operating due to the fact thatthe motor thereat is not running, station 5 transmits a group ofimpulses to cause the movement of blocking bar 66 to a position to blockthe operation of pull bars 49, while the blocking bar is in itsleft-hand position as viewed in Fig. 2. Following the completion of theintercommunication between stations 5 and I9, a predetermined codecombination of impulses is transmitted for operating the selector unitat the central station to cause the movement of pull bar 63, throughwhich bail 69 is operated, whereby the operated latches 59 are actuatedto release the operated bell crank levers 51 and contact I93 is openedmomentarily. The circuit and the apparatus is now restored to its normalposition.

Should a subscribed at station 6 desire to be connected to station 9 forthe purpose of communication with that station, transmitter T isoperated for transmitting a predetermined group oi code combinations ofimpulses which operate the-selector unit to select and operate the pullbar 99 allocated to the set of contacts individual to relays 99, which,through its right-hand contacts. controls the connection of lineconductor 9 in circuit with the line conductor extending to station 9.However, in order to operate relay 99 through contacts 59 controlled bythe operated bell crank lever 51, it is necessary that the selector unitbe in its upper case position in which contact spring 19 is inengagement with contact 99. Upon the energization of relay 94 in amanner similar to that described for relay 99, intercommunication may becommenced between stations 9 and 9. It is, oi course, assumed that priorto communication between such stations, a group of impulses wastransmitted preferably by station 9 to cause the operation of blockingbar 89 to prevent the further operation of pull bars 49 until a signalis transmitted for restoring the blocking bar 96 to the position shownin Fig. 2. Of course, if station 6 desires to communicate with stationsother than station 8, prearranged code combinations of impulses may betransmitted to the selector unit prior to the transmission of the groupof signals identified with the blocking bar for operating the pull barsidentified with such additional stations. The additional stations willbe connected in circuit with station 5 in a manner identical to thatdescribed for the other referred to stations. It is thus apparent thatstation 9 may communicate either with station 9 to the exclusion ofother stations or with any number of the other stations by thetransmission of the prearranged code combination of impulses identifiedwith such other staons.

From the previous description of the structure and its operation, it isevident that the line conductors of the various stations may beinterconnected directly through contacts 59, in which case relays 93,99, 95, 99, and 91 would not be required. In addition, the lockingcircuits for the noted relays may be eliminated with the provision ofthe mechanical latches 59. Of course, with the relays 93 to 91 inclusivearranged with locking circuits under the control of contact I93 operatedby lever B I, the mechanical latches 59 may be rotated about their pivotand held in a non-engaging position with respect to bell crank levers51. This may be achieved by the provision of an arm I95 pivoted to theside frame of the selector apparatus and arranged with instrumentalitiesfor holding it in its set position. With the apparatus so arranged, thebell crank levers 51 would be operated and the contacts 59 would bemomentarily closed for effecting the energization of the control relayindividual thereto, which would be locked up through contacts I93 andmaintained in that position pending the receipt of a signal combinationefiective to operate pull bar 63 and open normally closed contacts I93.

The invention has been disclosed and described in connection with aparticular form of apparatus. It is, however, manifest that other formsof apparatus might be used with equally good results without departingfrom the spirit and scope of the present invention, which is intended tobe limited only as set forth in the appended claims.

What is claimed is:

1. In a selector unit, a plurality of sets of contacts, means individualto each set of contacts for causing their operation, a plurality ofpermutation bars, means responsive to code signal impulses iorsettingsaid bars in varying permutations, a selectable element selected throughthe setting of said bars and operated upon its selection for operatingsaid contact operating means, means (or holding each contact operatingmeans in its actuated position, and means associated with saidpermutation bars and responsive to a particular setting thereof forpreventing, pending the, establishment oi predetermined signalconditions, the further operation of said contact operating means.

2. In a selector unit, a plurality of sets of contacts, means individualto each set oi contacts for causing their operation, a plurality ofpermutation bars, means responsive to code signal im-' pulses forsetting said bars in varying permutations, a selectable element selectedthrough the setting of said bars and operated upon its selection foroperating said contact operating means, a latch for each contactoperating means for holding it in its actuated position, and a blockingbar arranged with said permutation bars and operated in response to aparticular setting of said bars for preventing, until the selection oi.a particular selectable element, the operation of said other selectableelements.

3. In a selector unit, a plurality of sets of contacts, means individualto each set of contacts for causing their operation, a plurality oipermutation bars, means responsive to code signal impulses i'or settingsaid bars in varying permutations, a selectable element selected throughthe setting of said bars and operated upon its selection for operatingsaid contact operating means, and a bar arranged with said permutationbars and operated to one position by a particular selectable element toprevent the operation of certain oi said selectable elements, andoperated to another position by a selectable element to permit theselection and operation of all of said selectable elements.

4. In a selector unit, a plurality of sets of contacts, means individualto each set of contacts for causingtheir operation, a circuit controllereffective to control the effectiveness of said contacts, a plurality oi.permutation bars, means responsive to code signal impulses forsettingsaid bars in varying permutations, a selectable element selectedthrough the setting 01 said bars and operated upon its selection foroperating said contact operating means, and means operated by certain ofsaid selectable elements for controlling the position of said circuitcontroller and thus the eiiectiveness oi said contacts.

- 6. In a selector-unit, a plurality of sets of contacts, meansindividual to each set oi contacts for causing their operation, acircuit controller having its contacts arranged to be connected incircuit with said plurality of contacts, a plurality oi permutationbars, means'responsive to code signal impulses for setting said bars invarying permutations, a selectable element selected through the settingoi, said bars and operated upon its selection ior operating said contactoperating means, a further permutation bar, and means responsive toparticular code signal impulses tor operating said iurther permutationbar to operate said'circuit controller.

6. In a selector unit, a plurality or sets of contacts, means individualto each set contacts for causing their operation, a plurality ofpermutation bars, means responsive to code signal impulses for settingsaid bars in varying permutations, a selectable element selected throughthe setting of said bars and operated upon its selection for operatingsaid contact operating means, a motor for supplying power efl'ective tooperate the selected selectable elements, a transmitting cam shaft,transmitting contacts controlled by said cam shaft, a clutch throughwhich power is commimicated to said transmitting cam shaft, and anelectromagnet eii'ective when energized to render said clutch eii'ectivewhereby power is communicated from said motor to said transmitting camshaft.

7. In a selector system, a plurality of sets of contacts, meansindividual to each set oi contacts tor causing'their operation, aplurality of permutation bars, means responsive to code signal impulsesfor setting said bars in varying permutations, a selectable elementselected through the setting of said bars and operated upon its selec-'tion for operating said contact operating means,

a latch for each contact operating means for lay to normal.

WALTER J. ZENNER.

